The structural gene arrangement and transcript pattern within the adenovirus-2 genome has been defined for the early and late genes. Early gene products are associated with cell transformation and are being identified and characterized from a selection of virally transformed cell lines. The proteins defined by the abundant mRNA class expressed in differentiated chick muscle tissue culture cells have been identified. DNA cloning procedures have been used to isolate the individual genes for these proteins. The structure and organization of these genes are being studied. The role of mRNA structure in the efficiency of translation has been under investigation utilizing defined prokaryotic mRNAs as templates in a eukaryotic translational system. Structural features within the mRNA which are important for efficient ribosome binding and translation have been defined.